Abstract: An array processing system including a grid array of processing elements, each of which is surrounded by a group of nearest neighbor processing elements in the grid array, each of said processing elements including an input multiplexer having a multiplexer output line and a plurality of multiplexer input lines each of which is connected to a different member of the group of nearest neighbor processing elements for that processing element; an output demultiplexer having a demultiplexer input line and a plurality of demultiplexer output lines each of which is connected to a different member of the group of nearest neighbor processing elements for that processing element; and a control circuit, which responds to a broadcast control signal by electrically coupling the input multiplexer output line in that processing element to the output demultiplexer input line in that processing element.